The present invention relates to the field of blower wheels or impellers formed from composite materials and which can be present in any industrial ventilation equipment or installation.
More particularly, the present invention relates to a centrifugal or mixed flow impeller formed from composite materials comprising a series of vanes supported by an annular support structure formed from composite materials, and at least one reinforcing collar based on filament windings including reinforcing fibers, for example carbon fibers, the collar being disposed coaxially with and close to the rotational axis of the impeller to form an interior collar.
Still more particularly, the present invention relates to a composite material disk for a centrifugal or mixed flow impeller.
Impellers are routinely produced from composite materials, and are generally intended for use in a variety of industrial ventilating installations, such as axial flow air compressors or turbine engines.
In such known devices, the impeller is produced by injecting resin into a suitable mold, the mold already containing composite material fibers which are intended to reinforce the entire structure of the impeller. In this type of known technique, the centrifugal impeller obtained by injection molding constitutes a unitary assembly including: the axle, an annular support structure and the ventilation vanes disposed radially about that structure.
The disadvantages of this technique for producing centrifugal impellers lie primarily in the difficulty in holding the reinforcing fibers in the desired configuration during the injection operation. As a result, the production technique is complicated and difficult, multiplying production safety. measures and leading to the production of centrifugal impellers with reduced strength, in particular as regards the ventilation vanes.
Finally, resin injection is an expensive production technique as the fibers currently in use must in general be manually disposed in the mold. A partial solution to these problems that has been proposed is to improve methods for producing centrifugal impellers by injecting resin by attempting to reinforce the strength of the impellers so produced. In particular, reinforcing the resistance of the ventilation vanes to centrifugal loads and reinforcing their bond with the annular support structure has been proposed. The proposed improvements have consisted of producing reinforced zones or collars formed by filament windings of carbon fibers located at the base of the vanes and at their periphery.
Such measures have tended to reinforce the mechanical strength of certain zones of the impeller but have failed to provide a general solution to the problem of the mechanical strength of the impeller assembly as a whole. Further, the question of high production costs remains unanswered.
One of the objects of the present invention is to provide a novel centrifugal impeller produced from composite materials which overcomes the various disadvantages discussed above and the construction of which guarantees correct behavior as regards centrifugal forces, and controlled stiffness and deformation.
Another object of the present invention is to provide a novel centrifugal impeller of composite material which is capable of withstanding high peripheral rotational speeds and is formed from cheap, light unitary materials.
Yet another object of the present invention is to provide a novel centrifugal impeller of composite material in which the various elements of the composite materials of the impeller combine to contribute to the lightness and general strength of the impeller.
Yet another object of the present invention is to provide a novel centrifugal impeller of composite material with improved and easier balance.
Yet another object of the present invention is to provide a novel centrifugal impeller of composite material that is easier to balance in an improved manner.
In accordance with the present invention, these and other objects have now been realized by the invention of an impeller comprising a plurality of vanes, first and second coaxial disks formed from composite material on opposite sides of the plurality of vanes for fixing the vanes in position, whereby the impeller can rotate about an axis of rotation, and at least one reinforcing collar disposed coaxially with and adjacent to the axis of rotation to provide an interior collar therefor, the at least one reinforcing collar comprising reinforcing fibers. In a preferred embodiment, the reinforcing fibers comprise carbon fibers.
In accordance with one embodiment of the impeller of the present invention, each of the first and second coaxial disks includes a pair of outer layers and an intermediate zone, the intermediate zone comprising material having improved compressive strength. In a preferred embodiment, each of the pair of outer layers comprises an inner skin layer facing the vanes and an outer skin layer facing away from the vanes. Preferably, each of the inner skin layers includes a decreasing thickness moving in a direction radially outward from the axis of rotation and each of the outer skin layers includes a substantially constant thickness.
In accordance with one embodiment of the impeller of the present invention, the intermediate zone comprises a solid material.
In accordance with another embodiment of the impeller of the present invention, the intermediate zone comprises a hollow core material having a honeycomb structure.
In accordance with another embodiment of the impeller of the present invention, each of the outer skin layers and each of the inner skin layers comprises a stacked plurality of layers of synthetic fiber material. In a preferred embodiment, each of the stacked plurality of layers comprises a plurality of radial sections, the plurality of radial sections each being partially overlapping with its adjacent radial sections.
In accordance with another embodiment of the impeller of the present invention, the at least one reinforcing collar comprises first and second reinforcing collars associated with the first and second coaxial disks, respectively.
In accordance with another embodiment of the impeller of the present invention, the at least one reinforcing collar is at least partially surrounded by at least one of the outer skin layers and at least one of the inner skin layers.
In accordance with another embodiment of the impeller of the present invention, the impeller includes a first peripheral collar axially and peripherally disposed on the first coaxial disk and a second peripheral collar axially and peripherally disposed on the second coaxial disk, each of the first and second peripheral collars comprising reinforcing fibers. In a preferred embodiment, the reinforcing fibers comprise carbon fibers. Preferably, each of the pair of outer layers comprises an inner skin layer facing the vanes and an outer skin layer facing away from the vanes. In a preferred embodiment, each of the first and second peripheral collars is at least partially surrounded by at least one of outer skin layers and at least one of the inner skin layers.
In accordance with another embodiment of the impeller of the present invention, the impeller includes a first annular balancing zone peripherally disposed inwardly from the first peripheral collar and a second annular balancing zone peripherally disposed inwardly from the second peripheral collar, the first and second annular balancing zones including a perforatable material. In a preferred embodiment, the perforatable material comprises a synthetic foam.
In accordance with another embodiment of the impeller of the present invention, the plurality of vanes comprises a composite material. Preferably, the plurality of vanes have an H-shaped cross-sectional configuration. In a preferred embodiment, the plurality of vanes include an attack edge, a pressure face and a trailing edge with respect to the direction of rotation of the impeller, and the impeller includes metal guard members for the plurality of vanes comprising a peg disposed on the attack edge, and a first shim affixed to the pressure face and covering the attack edge of the plurality of vanes. Preferably, the first shim also covers the trailing edge of the plurality of vanes.
In accordance with another embodiment of the impeller of the present invention, the impeller includes a second shim affixed to one of the first and second coaxial disks and including a flange disposed on the pressure face of the plurality of vanes.
In accordance with another embodiment of the impeller of the present invention, the first and second coaxial disks include a plurality of depressions adapted to receive the plurality of vanes in order to facilitate the positioning thereof.
The objects of the present invention are achieved by providing a centrifugal impeller produced from composite materials comprising a series of vanes supported by an annular support structure of composite material and at least one reinforcing collar based on filament windings including reinforcing fibers, for example carbon fibers, disposed coaxially with and close to the rotational axis of the impeller to form an interior collar, and in which the support structure comprises at least two coaxial disks mounted one against the other to clamp and fix the vanes.